diff --git a/drivers/misc/thinkpad_acpi.h b/drivers/misc/thinkpad_acpi.h
index a6c285585863..440145a02617 100644
--- a/drivers/misc/thinkpad_acpi.h
+++ b/drivers/misc/thinkpad_acpi.h
@@ -386,7 +386,7 @@ static u8 fan_control_initial_status;
 static u8 fan_control_desired_level;
 static int fan_watchdog_maxinterval;
 
-struct mutex fan_mutex;
+static struct mutex fan_mutex;
 
 static acpi_handle fans_handle, gfan_handle, sfan_handle;